Planarity detection methods and apparatus for electrochemical mechanical processing systems

ABSTRACT

The methods and systems described provide for an in-situ detection of planarity of a layer that is deposited on or etched off the surface of a substrate. Planarity can be detected using various detection mechanisms, including optical, electrical, mechanical and acoustical, in combination with the electrochemical mechanical processing methods, including electrochemical mechanical deposition and electrochemical mechanical etching. Once planarity is detected, a planarity signal can be used to terminate or alter a process that has been previously initiated, or begin a new process. In a preferred embodiment, an optical detection system is used to detect planarity during the formation of planar conductive layers obtained by electrochemical mechanical processing.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is based on, and claims priority from, U.S.Provisional Application No. 60/265,413 filed Dec. 15, 2000 entitled“Disturbed Boundary Layer Materials Deposition Method and Apparatus.”

FIELD OF THE INVENTION

The present invention relates to the manufacture of semiconductorintegrated circuits and more particularly to planarity detection methodsand apparatus for use in planar deposition and etching of conductivelayers.

DESCRIPTION OF THE RELATED ART

Conventional semiconductor devices generally include a semiconductorsubstrate, usually a silicon substrate, and a plurality of sequentiallyformed dielectric interlayers such as silicon dioxide and conductivepaths or interconnects made of conductive materials. Copper and copperalloys have recently received considerable attention as interconnectmaterials because of their superior electromigration and low resistivitycharacteristics. The interconnects are usually formed by filling copperin features or cavities etched into the dielectric interlayers by ametallization process. The preferred method of copper metallizationprocess is electroplating. In an integrated circuit, multiple levels ofinterconnect networks laterally extend with respect to the substratesurface. Interconnects formed in sequential interlayers can beelectrically connected using vias or contacts.

In a typical process, first an insulating interlayer is formed on thesemiconductor substrate. Patterning and etching processes are performedto form features such as trenches and vias in the insulating layer.Typically the width of the trenches is larger than the width of thevias. Then, copper is electroplated to fill all the features. However,the plating process results in a thick copper layer on the substrate,some of which need to be removed before the subsequent step.

FIG. 1A shows an exemplary portion 8 of such plated substrate 9, forexample a silicon wafer. As shown in FIG. 1A, vias 10, 11 and 12 as wellas a trench 13 are formed in an insulation layer 14, such as a silicondioxide layer, that is formed on the substrate 9. The vias 10,12 and thetrench 13 as well as surface 15 of the insulation layer 14 are coveredand filled with a copper layer 16 through electroplating process.Conventionally, after patterning and etching, the insulation layer 14 isfirst coated with a barrier layer 18, typically, a TaN or Ta/TaNcomposite layer. The barrier layer 18 coats the vias and the trench aswell as the surface of the insulation layer to ensure good adhesion andacts as a barrier material to prevent diffusion of the copper into thesemiconductor devices through the insulation layer. Next a seed layer(not shown), which is often a copper layer, is deposited on the barrierlayer. The seed layer forms a conductive material base for copper filmgrowth during the subsequent copper deposition. As the copper film iselectroplated, the copper layer 16 quickly fills the vias 10, 12 butcoats the wide trench 13 and the surface 15 in a conformal manner. Whenthe deposition process is continued to ensure that the trench is alsofilled, a thick copper layer or overburden is formed on the substrate 9.Conventionally, after the copper plating, CMP process is employed toglobally planarize or reduce the thickness of the copper layer down tothe level of the surface of the insulation layer. However, a CMP processis a costly and time consuming process that reduces productionefficiency.

The adverse effects of conventional material removal technologies may beminimized or overcome by employing a processing approach that has theability to provide thin layers of planar conductive material on theworkpiece surface, or even provide a workpiece surface with no or littleexcess conductive material. These planar deposition and removalprocesses also have application in thru-resist processes employed in ICmanufacturing. In these applications plating is performed into holesopened in resist layers, onto the seed films exposed on the bottom ofeach hole or opening as will be discussed in more detail later.

The term of Electrochemical Mechanical Processing (ECMPR) is used toinclude both Electrochemical Mechanical Deposition (ECMD) processes aswell as Electrochemical Mechanical Etching (ECME), which is also calledElectrochemical Mechanical Polishing. It should be noted that in generalboth ECMD and ECME processes are referred to as electrochemicalmechanical processing (ECMPR) since both involve electrochemicalprocesses and mechanical action.

In one aspect of an ECMPR process, aworkpiece-surface-influencing-device (WSID) such as a mask, pad or asweeper is used during at least a portion of the electrotreatmentprocess when there is close proximity, either physical contact or aslight spacing, with physical contact preferred, and relative motionbetween the workpiece surface and the WSID. Descriptions of variousplanar deposition and planar etching methods i.e. ECMPR approaches andapparatus can be found in the following patents and pendingapplications, all commonly owned by the assignee of the presentinvention. U.S. Pat. No. 6,176,992 entitled “Method and Apparatus forElectrochemica Mechanical Deposition.” U.S. application Ser. No.09/740,701 entitled “Plating Method and Apparatus that Creates aDifferential Between Additive Disposed on a Top Surface and a CavitySurface of a Workpiece Using an External Influence,” filed on Dec. 18,2000, and U.S. application Ser. No. 09/961,193 filed on Sep. 20, 2001,entitled “Plating Method and Apparatus for Controlling Deposition onPredetermined Portions of a Workpiece”. These methods can deposit metalsin and over cavity sections on a workpiece in a planar manner. They alsohave the capability of yielding novel structures with excess amount ofmetals selectively over the features irrespective of their size, ifdesired.

In ECMD methods, the surface of the workpiece is wetted by thedeposition electrolyte which is also in fluid contact with an electrode(anode) and a potential is applied between the surface of the workpieceand the electrode rendering the workpiece surface cathodic. Thusdeposition takes place onto the workpiece surface. In ECME methods, thesurface of the workpiece is wetted by the deposition electrolyte or aspecial etching electrolyte, which is also in fluid contact with anelectrode (cathode) and a potential is applied between the surface ofthe workpiece and the electrode rendering the workpiece surface anodic.Thus etching takes place from the workpiece surface. Very thin planardeposits can be obtained by first depositing a planar layer using anECMD technique and then using an ECME technique on the planar film inthe same electrolyte by reversing the applied voltage. Alternately theECME step can be carried out in a separate machine and a differentetching electrolyte. The thickness of the deposit may be reduced in aplanar manner. In fact, an ECME technique may be continued until all themetal on the field regions is removed. It should be noted that a WSIDmay or may not be used during the electroetching process sincesubstantially planar etching can be achieved either way. However, ifWSID is used the process is referred to as ECME.

As stated above, in ECMD methods the surface of the workpiece is wettedby the electrolyte and is rendered cathodic with respect to anelectrode, which is also wetted by the electrolyte. This results inmaterial deposition on the surface of the workpiece. During ECMD, thewafer surface is pushed against the surface of the WSID or vice versawhen the surface of the workpiece is swept by the WSID. Planardeposition is achieved due to this sweeping action as described in theabove-cited patent applications.

As shown in FIG. 1B, ECMD process yields nearly planarized andrelatively thin deposition layers that cannot be obtained usingconventional electroplating techniques. In comparison to the surfaceshown in FIG. 1A, the surface of the copper layer 16 in FIG. 1B isrelatively planar and would need a shorter CMP process time. Further, ifthe plating process is stopped as soon as the planar layer is formed,i.e. a planar plating endpoint is reached, time for the plating as wellas CMP processes can be minimized. That this planar plating endpoint isreached has been determined by removing the substrate from the ECMDapparatus and measuring the thickness of the copper layer ex-situ to seeif the desired end point has been reached. Alternately, some “set-up”substrates are processed using different amounts of charge during planardeposition. By evaluating the results, the minimum amount of chargenecessary for a desired level of planarization can be determined.

In ECME processes the etching time necessary to remove substantially allof the top conductive material from the field regions is estimatedbeforehand by using set-up substrates. These approaches are timeconsuming and expensive and they reduce the throughput and repeatabilityof the processes.

Therefore, there is a need for effective and in-situ planarity and endpoint detection methods in ECMPR technologies.

SUMMARY OF THE INVENTION

The present invention advantageously provides an in-situ method andapparatus for determining the planarity of a layer.

In certain embodiments, the methods and systems described provide for anin-situ detection of planarity of a layer that is deposited on or etchedoff the surface of a substrate. Planarity can be achieved in a number ofmanners, including the elimination of surface roughness that is causedby variations in the top surface as a result of features or cavitiesdisposed below or a finer degree of planarity in which the surfaceroughness that can be tolerated is sufficiently less than that whichcould be present and still avoid surface roughness caused as a result ofbelow-disposed features.

Planarity can be detected using various detection mechanisms, includingoptical, electrical, mechanical and acoustical, in combination with theelectrochemical mechanical processing methods, including electrochemicalmechanical deposition and electrochemical mechanical etching. Onceplanarity is detected, a planarity signal can be used to terminate oralter a process that has been previously initiated, or begin a newprocess, as will be described further hereinafter.

In a preferred embodiment, an optical detection system is used to detectplanarity during the formation of planar conductive layers obtained byelectrochemical mechanical processing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features, aspects, and advantages will becomemore apparent from the following detailed description when read inconjunction with the following drawings, wherein:

FIG. 1A is a diagram illustrating a cross-sectional view of an exemplarysubstrate following deposition of material onto the surface of thesubstrate;

FIG. 1B is a diagram illustrating a cross sectional view of theexemplary substrate of FIG. 1 following a conventional ECMD process;

FIGS. 2A-2B are diagrams illustrating cross sectional side views of anexemplary ECMPR system according to a presently preferred embodimentused for processing workpieces such as wafers;

FIG. 3 is a diagram illustrating a partial perspective view of theexemplary ECMPR system having a planarity detection system secured tothe side walls;

FIG. 4 is a diagram illustrating a bottom view of the exemplary ECMPRsystem of FIGS. 2B and 3;

FIG. 5 is a diagram illustrating a top view of the exemplary ECMPRsystem including the planarity detection system;

FIG. 6 is a diagram illustrating a top view of the exemplary ECMPRsystem including an alternative exemplary planarity detection system;

FIG. 7 is a diagram illustrating an exemplary control system fordetection system according to aspects of the present invention includinga computer and an ECMPR controller;

FIGS. 8A-8C are diagrams illustrating a cross-sectional view of anexemplary substrate during an ECMD process incorporating an exemplarydetection process according to aspects of the present invention;

FIGS. 9A-9B are diagrams illustrating a cross-sectional view of anexemplary substrate during an ECME process incorporating an exemplarydetection process according to aspects of the present invention;

FIGS. 10A-10B are diagrams illustrating a cross-sectional view of anexemplary substrate during an ECMD process incorporating an exemplarydetection process according to aspects of the present invention;

FIGS. 11A-11B are diagrams illustrating view of an exemplary ECMPRsystem using an exemplary belt WSID and that incorporates a detectionsystem according to aspects of the present invention;

FIGS. 12A and 12C are diagrams illustrating views of an alternativeexemplary ECMPR system using an exemplary wand WSID and thatincorporates a detection system according to aspects of the presentinvention; and

FIG. 12B illustrates the exemplary wand WSID according to FIGS. 12A and12C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As will be described below, the present invention provides methods andsystems for an in-situ detection of planarity of a layer that isdeposited on or etched off the surface of a substrate such as asemiconductor. In the context of this application, planarity can bedescribed as having been achieved when a given layer no longer hassignificant roughness on the surface of the layer. Significant surfaceroughness can vary, depending on the application. In certainapplications, surface roughness that is caused by variations in the topsurface as a result of features or cavities disposed below are requiredto be eliminated. In other applications, a finer degree of planarity isnecessary, and thus the surface roughness that can be tolerated issufficiently less than that which could be present and still avoidsurface roughness caused as a result of below-disposed features.Planarity can be detected using various detection means such as optical,electrical, mechanical and acoustical. For electroetching applicationsin addition to planarity, the nature of the material on the workpiecesurface may also change, indicating planarity by detection of adifferent layer than the one being etched, as will be discussed later.Once planarity is detected, a planarity signal can be used to terminateor alter a process that has been previously initiated, or begin a newprocess, as will be described further hereinafter.

In a preferred embodiment, an optical detection system of the presentinvention will be used to detect planarity during the formation ofplanar conductive layers by an ECMPR approach. The preferred embodimentwill now be described using the example of fabricating copperinterconnects for integrated circuit applications. It should, however,be recognized that the planarity detection system of the presentinvention can be used during the filling process of the cavities on anyworkpiece with various electroplated materials such as Au, Ag, Ni, Pt,Pd, Fe, Sn, Cr, Pb, Zn, Co and their alloys with each other or othermaterials, for many different applications such as packaging, flat paneldisplays, magnetic heads and such. As will be exemplified below, some ofthese applications involve thru-mask deposition where the conductor isdeposited directly and selectively into features opened in insulators ormasks on workpiece surfaces rather than all over the surface of theworkpiece.

Reference will now be made to the drawings wherein like numerals referto like parts throughout. FIGS. 2A and 2B are schematic side views of anexemplary ECMPR system 100 used for processing wafers. In FIG. 2A, aworkpiece-surface-influencing device (WSID) 102, which may or may nothave openings 104 in it, is disposed in close proximity of a workpieceor wafer 106 to be processed. In this embodiment, the WSID 102 may besupported by the sidewall 105 of an electrolyte container 107. As willbe exemplified below, WSIDs can have different configurations. WSIDs canbe designed as a pad or shaping plate, belt, wand or wiper, or otherconfigurations. The wafer 106 may be a silicon wafer to be plated with aconductor metal, preferably copper or copper alloy. The wafer 106 isretained by a wafer carrier 111 so as to position front surface 112 ofthe wafer against top surface 113 of the WSID 102. The openings 104 aregenerally designed to assure uniform application of solution, depictedby arrows 114, onto the front surface 112. Instead of discrete openings,a WSID that is porous may also be used, in which case the opening arethe pores. In special circumstances, a specific deposit thicknessprofile such as an edge-thick profile or an edge-thin profile may bedesired. In these cases the openings 104 are designed to yield theseprofiles. As the name suggests in edge-thick profile the thickness ofthe conductive material gets larger going from the center towards theedge of the workpiece. In edge-thin profile the reverse is true.

In any case, the top surface 113 of the WSID 102 facing the frontsurface 112 of the wafer is used as the sweeper and the WSID 102 itselfestablishes good electrolyte flow and electric field flow to the frontsurface 112 for controlled deposition or etching. ECMPR system 100 alsoincludes an electrode 116, which is immersed in the solution 114 that iscontained in the container 107. The solution 114 is in fluidcommunication with the electrode 116 and the front surface 112 of thewafer 106 through the openings 104 in the WSID 102. The electrode 116 istypically a Cu piece for ECMD of copper films or the electrode 116 mayalso be an inert electrode made of, for example, Pt coated Ti,particularly in an ECME application.

An exemplary solution 114 that is particularly usable in ECMDapplications of copper or combined ECMD and ECME applications of coppermay be a copper electrolyte solution of copper sulfate with additivessuch as accelerators, suppressors, and chloride ions, which are commonlyused in the industry. Additionally, levelers may be added in smallquantities, although ECMD process does not typically need leveler sinceit does leveling of the deposited film automatically. Leveler may beadded, if needed, however, for optimization of other process resultssuch as gap fill etc. The top surface 113 of the WSID 102 sweeps thefront surface 112 of the wafer while an electrical potential isestablished between the electrode 116 and the front surface 112 of thewafer. For deposition of a planar film such as copper, the front surfaceof the wafer 102 is made more cathodic (negative) compared to theelectrode 116, which becomes the anode. The surface of the WSIDpreferably contains hard-abrasive material for efficient sweeping. Fixedabrasive pads which are supplied by companies such as 3M and which arecommonly used in CMP applications work efficiently on WSID surfaces. Forelectroetching in the same ECMPR system, the wafer surface is made moreanodic than the electrode. For ECME processing without ECMD, thesolution 114 may preferably be an etchant.

As stated above, during the ECMPR an electrical potential is establishedbetween the front surface of the wafer and the electrode. In order toestablish this potential, as shown in FIG. 2B, the front surface 112 ofthe wafer is connected to a power source (not shown) through contacts118 touching and sliding on a peripheral region 120 of the front surface112 of the wafer 106. In order to expose the peripheral region 120 asthe wafer is rotated, in one embodiment, the width of the WSID is keptshorter than the diameter of the wafer 106.

The planarity detection method of one of the preferred embodiments ofthe present invention involves detection of a change in reflected lightintensity, which intensity change is associated with a change in theplanarity of the substrate. In this embodiment, by employing suitabledetection devices, the detection process may be performed on wafer 106as it is plated, such as at the peripheral edge region 120 of the wafer106. If the WSID is of a type that covers a substantial portion of thewafer 106, openings within the WSID can be used to perform detection onthe portion of the wafer that is below the openings. In the case of adetection process that uses light, for example, light can pass throughan opening or openings, through the solution, be reflected off of thewafer 106, and again pass through the solution and the opening oropenings and then be detected. If a portion of the wafer 106 needs to beexposed and an opening or openings do not exist in the WSID, thisexposure can occur by having a portion of the wafer 106 not covered theWSID, or relatively moving the wafer 106 and the WSID with respect toeach other to expose a portion of the wafer 106 for detection.

As shown in FIG. 2B and in partial perspective view in FIG. 3, aplanarity detection system 122 may be secured on the side walls 105 ofthe container, below the WSID 104, or secured in a location below thelevel of the wafer surface by any other mean. The detection system 122may have at least one light source 124 and at least one light sensor 126as can be seen in FIG. 3 which is a view in the direction “dir”indicated by arrow in FIG. 2B. The light source 124 generates an opticalbeam 128 to impinge the front surface 112 at an impingement zone 130,with an incidence angle “α”. Depending on the nature of the input beamthe impingement zone can be very small or relatively large. It maytypically change from 1 mm² to 1 cm². Similarly, the angle “α” may bevery small. In fact, typical systems have light source 124 and lightsensor 126 in a single body right next to each other. These systemsmeasure vertical or near vertical reflection from the substrate surface.For ease of explaining and illustration, however, the angle will beillustrated as the relatively large angle “α” as shown in FIG. 3. Theinput optical beam 128 is reflected by the front surface and forms areflected or output optical beam 132. The output beam 132 is received bythe sensor 126 of the detecting system 122 and will produce a signalassociated with the sensed reflected beam at various points in time thatis used determine planarity. In particular, the signal containsinformation indicative of the planarity of the top conductive layer,typically an intensity value that exceeds a predetermined thresholdvalue.

In this embodiment, the source 124 and the sensor is preferably locatedsymmetrically around a surface axis 134, which surface axis 134 isnormal to the surface 112 at impingement zone 130. As shown in a bottomview, in FIG. 4, it will be appreciated that the impingement zone is nota fixed region on the surface, rather it may be for example a point on afirst sampling track 136 and a second sampling track 138. The secondsampling track 138 represents the straight sampling route that the inputbeam impinges on as the wafer 104 is moved laterally. The first samplingtrack 136 represents the circular sampling routes followed by theimpinging beam when the wafer 104 is rotated either applying a lateralmotion or not. If both motions, lateral and rotational, are giventogether, the peripheral edge region 120 is completely scanned.

Referring back to FIG. 3, the input beam is projected from the source124 at an angle of incidence α from the surface axis 134. The angle ofincidence α may be in the range of 0-60 degrees. The light source ispreferably one that generates a beam of white light and a the sensorsenses the intensity of the reflected white light. It is also possibleto use a white light nput, but a sensor that measures only apredetermined wavelength of the reflected white light. Alternatively,the light source may generate a beam of light with a predeterminedsingle or multiple wavelengths, and the sensor may be provided to sensethe intensity of the sensed light at least at that predeterminedwavelength or multiple wavelengths. The single wavelength used ispreferably that wavelength providing the highest signal for the materialbeing planarized, as each material reflects different wavelengthsdifferently.

As shown in FIG. 5 in top view, alternatively, the ECMPR system 100 maybe so equipped that the wafer 106 may be periodically moved over thedetection system 122 to monitor a central region 139 of the wafer duringthe process in addition to the monitoring of the edge regions asexplained before.

As illustrated in FIG. 6, an alternative detection system 140 maymonitor the peripheral and central regions 120, 139 at the same time.The system 140 may comprise a first set of detection means 141 and asecond set of detection means 142. The first set of detection means 141comprises a first light source 143 and a first sensor 144, and thesecond set of detection means 142 comprises a second light source 145and a second sensor 146. During the operation, the first set ofdetection means 141 monitors the edge region 120 of the wafer while thesecond set of detection means 142 monitors the central region 139 of thewafer 106. Other variations of placing the planarity detection systemsin the ECMPR system are also within the intended scope of the invention.

In use, ECMPR system 100 may use the exemplary detection system 122 todetermine if the desired end-point of a particular process is reached.The desired endpoint is typically the point where the deposited layer isplanar, so that another process can then be initiated, though that isnot necessarily the case. Alternately, the desired end point may be whenthe excess metal is etched off from a non-planar surface of theworkpiece, or when excess metal is etched off until a layer disposedbelow the metal being etched is exposed.

In any case, as shown in FIG. 7, the detection system can be connectedto a computer 147 which computer is also connected to a ECMPR controller148, although it is understood that the computation could be performedin many manners, and need not necessarily require a computer with aprocessor, but instead could use discrete or integrated logic circuits,including but not limited to ASICS and programmable gate arrays. Duringoperation, when the desired planarity or end-point is reached, thedetector output signal from the detector 122 changes. Thus, bycontinuously monitoring the detector output signal, the computer 147 cangenerate a planarity or endpoint signal and provide that signal to theECMPR controller 148 to halt the particular ECMPR process at theappropriate time. Another process may then take place.

One embodiment of the detection process of the present invention basedupon plating using ECMD will now be described with the help of FIGS. 8Athrough 8C. FIG. 8A shows a portion of the wafer 106 and a front surface112 in a highly magnified state. The front surface 112 of the wafer 106typically includes an insulating layer 150, such as silicon oxide, whichis etched and patterned to form features such as vias 152 and trenches154. The insulating layer 150 is also coated with a barrier layer Ta orTaN and then coated with a copper seed layer, which are not shown forthe purpose of clarity. It should be noted that the invention is usableeven for the case of filling features opened in a conductive rather thaninsulating surfaces for other applications. As shown in FIG. 8A, thecolumnated input beam from the source 124 arrives at the front surface112 and is reflected. Since the front surface 112 is rough due to thepresence of the vias and trenches and other features, the reflected oroutput beam is not columnar but is rather scattered. Only a portion ofthe output beam 132 reaches the sensor 126. Therefore, intensity of thereflected beam that can be detected by the sensor 126 is very low. Sincethe input beam has a predetermined intensity, an intensity loss, whichis detected by the sensor 126, indicates the surface roughness. The ECMDprocess is initiated to plate copper onto the front surface 112. Asshown in FIG. 8B, as a copper layer 156 fills the features 152, 154 andcovers the front surface 112, more of the output beam 132 arrives at thesensor 126. Thus, the intensity difference between the input beam andthe output beam is not as large as in the previous case shown in FIG.8A. As shown in FIG. 8C, however, as the copper layer becomes planar,indicating that features are filled in if that is the planarity desired,the output beam 132 that is detected by the sensor 126 substantiallyincreases, indicating planarization has been achieved and that theend-point has been reached. At his time, the ECMD process is halted.Another process, such as ECME or CMP can then be initiated, if desired.

FIGS. 9A-9B illustrate an alternative detection system 160 that is usedduring an ECME process which is employed to etch a conductive layer orlayers. As shown in FIG. 1A, features 166 and 168 are etched intoisolation layer 164. A barrier layer 169 such as Ta or TaN, and a copperseed layer (not shown) are then coated over the surface. A copper layer170 fills the features and covers substrate 162. The copper layer 170may have been obtained as a result of conventional depositiontechniques, or a combination of ECMD and conventional depositiontechniques. The detection system 160 comprises a light source 172generating an input beam 174 and a sensor 176 to receive reflected oroutput beam 178. In this embodiment the sensor 176 also measures changein the intensity of the reflected beam.

If the starting film is not planar and only planarity is desired as aresult of ECME process, then the sensor 176 can operate as describedabove with respect to deposition of a material, such that once thedesired degree of planarity is achieved, the reflected beam intensityincreases and the process can be halted.

If, however, removal of a layer is desired, then the opticalreflectivity characteristics of the barrier material and the copper,which are different, can be used so that the sensor 176 canadvantageously detect the barrier layer, which exposure provides theendpoint. As shown in FIGS. 9A-9B, as the copper layer 170 is etchedback in a planar fashion using ECME, the intensity difference betweenthe input and output beams is minimal, which suggests etching is planarand the material is still copper. In FIG. 9A, before the exposure of theunderlying barrier layer, detected reflectivity characteristics of thecopper layer 170, from the output beam 178, approximates a constantvalue. However, once the barrier layer is exposed, as shown in FIG. 9B,detected reflectivity characteristics abruptly changes, indicating theexposure of barrier layer 169. For example using a light with awavelength of about 690 nm, reflected light intensity drops as materialschanges from Cu to Ta.

The present invention can also be used during manufacture of conductivenetworks requiring formation of narrow and large gaps through a masklayer coated on a substrate and filling them with a conductive materialsuch as copper using the ECMD process. One such example is described inU.S. application Ser. No. 10/282,976, entitled Method and Structure forThru-Mask Contact Electrodeposition, filed on Oct. 28, 2002, owned bythe assignee of the present invention. As shown in FIGS. 10A-10B, asubstrate 180 is first coated with a barrier layer 182 and then with acopper seed layer 184. A resist layer 186 is formed on the seed layer184 and defined and etched to form various features such as vias 188 andtrenches 190. The resist material may be soft or hard baked organicmaterials, it could be inorganic materials such as silicon oxide,alumina, sapphire or another material. The resist material may also be alow or high dielectric constant material. In the context of thisembodiment, a resist material is hereby defined as that material thatcopper or any metal of interest will not nucleate on without a seedlayer coating. Similar to the embodiment described with FIGS. 8A-8C,FIG. 10A shows features that are partially filled using the ECMDprocess. In this embodiment as the features 188, 190 are filled with acopper layer 191, input beam 192 from a source 194 arrives at thesurface of the substrate under the same angle of incidence, with a knownintensity. Because of the surface roughness, output beams 196 arerandomly scattered and only a few beams are detected by the sensor 198.Therefore, if the input beam 192 has a predetermined intensity, theintensity loss, which is detected by the sensor 198, indicates thesurface roughness. The ECMD process is continued to plate copper. Asshown in FIG. 10B, as a copper layer completely fills the features andthe copper layer 191 becomes planar, the intensity of the output beam196 that is detected by the sensor 198 increases. Once the planarsurface is obtained, the ECMD process is halted.

As shown in following FIGS. 11A-12C, the detection system and process ofthe present invention may be used with various ECMPR systems utilizingvarious WSID designs.

FIGS. 11A-11B shows an ECMPR system 200 using a belt WSID 202. Anexample of such belt WSID is described in U.S. application Ser. No.10/288,558, entitled Electrochemical Mechanical Processing withAdvancible Sweeper, filed Nov. 4, 2002, commonly owned by the assigneeof the present invention. The belt WSID 202 is extended between a supplyspool 204 and storage spool 206 and moved by a moving mechanism (notshown). During the process, a wafer 208 is held by the carrier head 210in close proximity of the belt WSID such that a process solution 212,such as an electrolyte, flowing through a porous support plate 213 andchannels 214 in the belt WSID wets the front surface of the wafer. Theprocess solution and an electrode 215 that is immersed in the solutionare kept in a container 216. The wafer processed over a predeterminedarea or a process area 218 of the belt WSID. As the belt is tensionedover an upper surface of the porous support plate, a top compressiblelayer 220 of the support plate pushes the belt upward. The process areais renewed by advancing the belt WSID such that a used process area isreplaced by a fresh process area by rolling the used process area overthe storage spool and thereby drawing fresh process area from the supplyspool. During the process, the wafer carrier can move the wafer on orabove the belt WSID laterally and rotate about the rotation axis z ofthe wafer carrier. The belt WSID of the present invention can also bemoved laterally while the wafer is moved on it by the carrier head.

In this embodiment, a planarity detection system 230 may be secured onthe side walls 232 of the container, below the belt WSID 104. Thedetection system 230 may have at least one light source 234 and at leastone light sensor 236. The light source 234 generates an input opticalbeam 238. The input optical beam 238 is reflected by the front surfaceof the wafer and as an output optical beam 240. The output beam 240 isreceived by the sensor 236 of the detecting system 230.

FIGS. 12A-12C illustrate an alternative ECMPR system 250 having anelectrode 252 and an electrolyte 254 which are kept in a container 256.There may also be a diffuser 258 or shaping plate in between theelectrode 252 and a wafer 260 to be processed (cathode) to assist inproviding a uniform film deposition on the wafer 260. The shaping plate258 will typically have openings that control fluid and electric fielddistribution over the wafer surface. The wafer 260 is held by a waferholder 262. In this embodiment of the present invention, a wand WSID 264is positioned in close proximity to the wafer. During processing, theWSID 264 makes contact with the top surface of the wafer, sweeping it sothat during at least part of the time copper deposition orelectroetching is performed. The WSID may have openings 265 in itallowing electrolyte flow. The WSID 264 may be of any size and shape andmay have a handle 268 that moves the WSID on the wafer surface,preferably using programmable control, and can also be retractable sothat it moves the sweeper entirely off of the area above the top surfaceof the wafer.

In this embodiment, a planarity detection system 270 may be secured onthe WSID 264 as in the manner shown in FIGS. 12B-12C. The detectionsystem 270 may have at least one light source 274 and at least one lightsensor 276. The light source 274 generates an input optical beam 278.The input optical beam 278 is reflected by the front surface of thewafer and as an output optical beam 280. The output beam 280 is receivedby the sensor 276 of the detecting system 270.

In any of the above embodiments, the planar endpoint detection may beperformed in a timed fashion to determine the approximate time span thatthe endpoint is reached for a specific process. This time informationcan be further used to monitor other process variables that has effecton the planarity of the layer such as additives in the process solution.For example, during the sequential processing of a group of similarsubstrates, the time required to reach the planarity endpoint can beexperimentally determined as time t_(p). If a process cycle for aspecific substrate exceeds the time t_(p) without reaching at theplanarity endpoint, this may for example indicate variations in theprocess additives.

Although various preferred embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications of the exemplary embodiment are possible withoutmaterially departing from the novel teachings and advantages of thisinvention.

1. A method for detecting planarization of a top surface of a workpiecewith features in an electrochemical mechanical deposition process thatuses a solution containing a conductor therein and operates upon the topsurface comprising: depositing the conductor to fill the features withinthe top surface of the workpiece using electrochemical mechanicaldeposition employing a workpiece surface influencing device, an appliedpotential and the solution; transmitting a beam of light onto the topsurface of the workpiece to obtain a reflected beam of light, acharacteristic of the reflected beam of light being altered by a topsurface pattern that exists due to the features within the top surfaceof the workpiece; and detecting, during electrochemical mechanicaldeposition, a change in the characteristic of the reflected beam oflight indicative of a degree of planarization to the top surface of theworkpiece.
 2. The method according to claim 1 further including the stepof terminating the electrochemical mechanical deposition at apredetermined degree of planarization.
 3. The method according to claim2 further including a material removal step.
 4. The method according toclaim 3 wherein the material removal step performs chemical mechanicalprocessing.
 5. The method according to claim 3 wherein the materialremoval step performs electrochemical mechanical polishing and furthercomprises the steps: transmitting another beam of light onto the topsurface of the workpiece to obtain another reflected beam of light; anddetecting a change in a characteristic of the another reflected beam oflight indicative of a another material on the top surface of theworkpiece.
 6. The method according to claim 5 wherein the beam of lightand the another beam of light are from a same source.
 7. The methodaccording to claim 1 wherein the characteristic is intensity of thereflected beam of light.
 8. The method according to claim 1 wherein thebeam of light transmitted onto the top surface of the workpiece passesthrough the workpiece surface influencing device.
 9. The methodaccording to claim 8 wherein the characteristic is intensity of thereflected beam of light.
 10. The method according to claim 1 wherein thebeam of light transmitted onto the top surface of the workpiece isadjacent to the workpiece surface influencing device.
 11. The methodaccording to claim 10 wherein the characteristic is intensity of thereflected beam of light.
 12. A method for detecting planarization of atop surface of a workpiece in an electrochemical mechanical depositionprocess that uses a solution containing a conductor therein, the methodcomprising: electrochemically mechanically depositing the top surface ofthe workpiece using a workpiece surface influencing device, an appliedpotential and the solution to deposit material onto the top surface;transmitting a beam of light onto the top surface of the workpiece toobtain a reflected beam of light; and detecting, duringelectromechanical depositing, a change in a characteristic of thereflected beam of light indicative of a degree of planarization to thetop surface of the workpiece.
 13. The method according to claim 12further including the step of terminating the electrochemical mechanicalprocess at a predetermined degree of planarization on of the topsurface.
 14. The method according to claim 13 further including the stepof removing at least a portion of the material.
 15. The method accordingto claim 14 wherein the step of removing performs chemical mechanicalprocessing.
 16. The method according to claim 14 wherein the step ofremoving performs electrochemical mechanical polishing and furthercomprises the steps: transmitting another beam of light onto the topsurface of the workpiece to obtain another reflected beam of light; anddetecting a change in a characteristic of the another reflected beam oflight indicative of a another material on the top surface of theworkpiece.
 17. The method according to claim 14 wherein the step ofremoving performs electrochemical mechanical polishing.
 18. The methodaccording to claim 12 wherein portions of the top surface is conductiveand the step of electrochemically mechanically processing deposits aconductor into features disposed in the top surface of the workpiece.19. A method for detecting planarization of a top surface of a workpiecehaving a plurality of features comprising: depositing the conductor tofill the features within the top surface of the workpiece usingelectrochemical mechanical deposition; and obtaining a signal indicativeof a degree of planarity of the top surface during electrochemicalmechanical deposition.
 20. The method according to claim 19 wherein tothe step of obtaining comprises: transmitting a beam of light onto thetop surface of the workpiece to reflect the beam of light; and detectinga characteristic of a reflected beam of light from the top surface; andtransforming the characteristic into a signal which corresponds to thedegree of planarity of the top surface.
 21. The method according toclaim 20 further including the step of terminating the step ofdepositing when the planarity of the top surface reaches a predetermineddegree.
 22. The method according to claim 21 further including amaterial removal step.
 23. The method according to claim 22 wherein thematerial removal step performs electrochemical mechanical processing.24. The method according to claim 22 wherein the material removal stepincludes: transmitting another beam of light onto the top surface of theworkpiece to obtain another reflected beam of light; and detecting achange in a characteristic of the another reflected beam of lightindicative of another material on the top surface of the workpiece. 25.The method according to claim 20 wherein the characteristic is intensityof the reflected beam of light.
 26. The method according to claim 25wherein the intensity increases as the surface of the workpiece becomesmore planar.
 27. The method according to claim 1 wherein the conductoris copper.
 28. The method according to claim 5 wherein the conductor iscopper.
 29. The method according to claim 5 wherein the another materialis a barrier material.
 30. The method according to claim 7 wherein theintensity increases as the degree of planarization increases.
 31. Themethod according to claim 9 wherein the intensity increases as thedegree of planarization increases.
 32. The method according to claim 14wherein the step of removing performs chemical mechanical polishing andfurther comprises the steps: transmitting another beam of light onto thetop surface of the workpiece to obtain another reflected beam of light;and detecting a change in a characteristic of the another reflected beamof light indicative of another material on the top surface of theworkpiece.